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Research says TB infection may be underestimated among people taking corticosteroid pills

26.06.2014

More screening may be needed

Tuberculosis infection among people taking corticosteroid pills may be underestimated, new research suggests. Current guidelines for what constitutes a positive TB skin test among corticosteroid pill users may not be capturing all those who are infected, said

Current guidelines for what constitutes a positive TB skin test among corticosteroid pill users may not be capturing all those who are infected, said Dr. Nicholas Vozoris, a respirologist in the Tuberculosis Program at St. Michael's Hospital.

Credit: Courtesy of St. Michael's Hospital

Dr. Nicholas Vozoris, a respirologist in the Tuberculosis Program at St. Michael's Hospital.

Previous research has shown that people who take corticosteroid pills, such as Prednisone, and have inhaled the TB bacteria, have an eight times higher risk of the bacteria becoming active than people who are not taking the drugs.

Dr. Vozoris said that would suggest they should be screened more often for TB infection.

However, an examination of more than 7,300 people in the U.S. National Health and Nutrition Examination Survey found this was not the case. The survey, a series of studies designed to assess the health and nutritional status of adults and children in the United States, is unique in that it combines interviews and physical examinations.

The findings were published today in the European Respiratory Journal.

He found that although taking corticosteroid pills was a risk factor for turning latent TB into active TB, those patients were screened less often for TB than others. They were also less likely to be prescribed TB-fighting drugs prophylactically.

Dr. Vozoris said that for the general population, producing a bump at least 10 millimetres in diameter following a TB skin test likely means that one has inhaled the TB bacteria. Current guidelines recommend that the bump be only five millimetres long if the patient is taking corticosteroid pills, but Dr. Vozoris said there is no evidence to support that is the correct cut-off. The study results show that 3.5-mm might be a more appropriate cut-off.

Corticosteroid pills are commonly prescribed for people with asthma, chronic obstructive pulmonary disease, inflammatory bowel disease, inflammatory arthritis and cancer. They work by decreasing inflammation, but they also suppress the immune system.

The Respirology Division of St. Michael's Hospital has a Tuberculosis Program dedicated exclusively to caring for patients with TB disease and infection. The program's clinic has 1,900 patient visits a year, making it one of the largest TB clinics in Canada.

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About St. Michael's Hospital

St. Michael's Hospital provides compassionate care to all who enter its doors. The hospital also provides outstanding medical education to future health care professionals in 27 academic disciplines. Critical care and trauma, heart disease, neurosurgery, diabetes, cancer care, care of the homeless and global health are among the hospital's recognized areas of expertise. Through the Keenan Research Centre and the Li Ka Shing International Healthcare Education Centre, which make up the Li Ka Shing Knowledge Institute, research and education at St. Michael's Hospital are recognized and make an impact around the world. Founded in 1892, the hospital is fully affiliated with the University of Toronto

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